68 



Sir W. Thomson on an Electric Machine 



ively with the inductors; and the other two (called connecting 

 springs) are insulated and connected with one another (one of 



Fig. 2. 



the inductors is generally connected with the earth, and the other 

 insulated). They are so situated that they are touched by the car- 

 riers on emerging from the inductors, and shortly after the con- 

 tacts with the receiver-springs. If any difference of potential 

 between the inductors is given to begin with, the action of the 

 carriers, as is easily seen, increases it according to the compound- 

 interest law as long as the insulation is perfect. Practically, in 

 a few seconds after the machine is started running, bright flashes 

 and sparks begin to fly about in various parts of the apparatus, 

 even although the inductors and connectors have been kept for 

 davs as carefully discharged as possible. Forty elements of a 



